There is such a conventionally known condenser including a cooling section in which a large number of narrow passages for cooling medium such as air and a large number of narrow vapor passages are disposed alternately.
If the vapor passages are narrow, however, there is a possibility that the following disadvantage may be encountered: the operating medium in the liquid-phase state produced in such passages, e.g., water occludes the passages due to factors such as a surface tension of the operating medium and as a result, the amount of water vapor flowing in the cooling section is reduced, resulting in a reduction in condensing performance.